Burner control apparatus and protection system



Dec. 17, 1940. B, H W 2,225,237

BURNER CONTROL APPARATUS AND PROTECTION SYSTEM Filed Sept. 11/1959 by acover 12.

Patented Dec. 17, 1940 UNITED STATES PATENT OFFICE BURNER CONTROLAPPARATUS AND PROTECTION SYSTEM Burton E.

Shaw, Bristol, Ind., assignor to Penn Electric Switch 00., Goshen, Ind.,a corporation of Iowa Application September 11, 1939, Serial No.294,410Claims. (Cl. 15828) tinuation in part of my copending application,

Serial No. 179,706, filed December 14, 1937.

Another object is to provide a control apparatus for burners of any typehaving blowers and which, therefore, if the blower operates properly,produces a vacuum, a safety switch being provided in connection with theapparatus to aiford protection against explosions and the like and beingcontrolled in response to the suction of the induction blower. I

A further object is to provide. control apparatus and a control circuitarrangement therefor,

whereby a suction switch of the control apparatus is operable to controla safety switch thereof, so that if suction fails initially or if itfails subsequent to being established, the safety switch will operate tode-energize the control circuit and thereby stop operation of the burnerand induction blower, combustion failure effecting, stoppage of the flowof fuel to the burner by conventional control devices which do not formany part of my present invention.

With the foregoing'and other objects in view, which will become apparentas the description proceeds, my invention consists in the construction,arrangement and combination of the various 3 parts thereof, whereby theobjects as above contemplated are attained, as hereinafter more fullyset forth, pointed out in the appended claims and illustrated in theaccompanying drawing, in

which Figure 1 is a sectional view showing details of a suction switchused in my burner control apparatus and protection system; and

Figure 2 is a circuit diagram for my control apparatus and protectionsystem.

On, the accompanying drawing I have used the reference numeral 1 II toindicate generally a housing formed of sheet metal or the like. Thehousing .10 is preferably closed against the entrance of dust ortampering of the mechanism therein V The suction switch of my controlapparatus is indicated generally in Figure 2 as Sue. S. It comprises apair of switch arms and 5| (see Figure 1) and a disc 52 for operatingthem. Normally, the switch arms are retained in contact with each otherby a spring 53 urging a rod 54 outwardly. The rod 54 has a hub 55secured thereto which carries a disc 56. The disc 56 engages the switcharm 50. The disc 52 is mounted in and substantially spans a section ofconduit 51.

The conduit 51 is connected by a conduit 58 to the intake 59 of aninduction blower B (see Figure 2). Accordingly whenever the blower Boperates, a vacuum will be created in the conduit 51 which will suck thedisc 52 inwardly against the bias 10 of the spring 53 to the dottedposition shown in Figure 1. In this position the hub 55 engages a feltwasher 60 which prevents shock to the parts and also prevents vibrationof the disc 52' while subject to the suction of the blower. In thedotted 15 position, the disc 56 permits the switch arm 50 to separatefrom the switch arm 5 I, thus opening the circuit through the suctionswitch Suc. S. In Figure 2, I show diagrammatically a relay coil RCoperatively connected with a motor switch MS. The parts RC and MScomprise a relay, which relay also includes a holding switch HS. Theholding switch and the motor switch are normally open but close when therelay coil RC is energized. A safety switch SS is more or lessconventional, and comprises a safety switch heater SSH, a bimetal latch48 and a switch arm 49. The latch 48 normally holds the arm 49 in closedcircuit position while a predetermined period of energization of thesafety switch heater SSH results in warping oi" the bimetal latch 48 toa position permitting the safety switch SS to open.

The various control devices thus far described are includedin acontrolcircuit energized by the secondary of a transformer T. Thiscircuit includes a limit switch LS and a room thermostat RT while themotor switch MS is included in the power circuit of the blower motor M.The motor M is illustrated as being belted as by a power transmissionbelt 6| to the induction blower B. The blower furnishes air to theburner of the furnace.

My control system as thus far described does not includemeans for takingcare of combustion failure either initially orsubsequent to combustionestablishment. My system is included in a conventional burner controlinstallation that already has such protection, and such conventionalinstallation may include ignition mechanism consisting of a gas valveGV, a pilot light M, a thermostat l5 and a gas valve switch 16. The gasvalve GV when open supplies gas to a burner 11. The heat from the burnerl1 and/or fromthe pilot flame l8 normally keeps the thermostat l5 in theposition illustrated with the switch l6 closed. The switch It is inseries with the gas valve GV and in series with the mrotor switch, thuspermitting gas to flow to the burner I! only when the motor M isoperating.

Practical operation In the operation of my burner control apparatus andprotection system, the parts are normally in the position of Figure 2.When the room thermostat RT calls for heat, its contacts close. Thisestablishes an initial room thermostat circuit through the followingwires and elements of the circuit, the wires being indicated by lowercase letters. From the lower end of the transformer secondary coilthrough :1, LS, b, RT, 0, SS, d, RC, e, f, SSH, i, Suc. S. and j, to theupper end of the secondary coil.

This initial room thermostat circuit causes energization of the relaycoil which closes the holding switch HS and the motor switch MS. Closureof the holding switch alters the character of the initial roomthermostat circuit so 1 that instead of -a single circuit there is thena pair of circuits which I will designate as second and third circuits.The second circuit is from the lower end of the secondary coil throughthe following wires and elements: 0, LS, b, RT, 0, SS, d, RC, 6, k, HSand 1, tea center tap 62 of the transformer secondary.

The third circuit is from the center tap 62 through the following wiresand elements: I, HS, in, f, SSH, 2', Sue. S, and 7' to the upper end ofthe transformer secondary. The second and third circuits thusestablished provide for low voltage protection of the control system ina manner fully set forth in my Ratent No. 2,080,580, of May 18, 1937,and accordingly will not be gone into in more detail in the presentapplication. It should be mentioned, however, that the second circuitthus established provides a holding circuit for the relay coil RC whilethe .third circuit is provided for the safety switch heater SSH and canbe opened without de-energizing the relay coil.

Closure of the motor switch MS causes the motor M to operate andlikewise the blower B to operate. Operation of the blower will by thetime the motor gets up to speed, have produced enough vacuum in theconduits 51 and 58 to cause the disc 52 to open the suction switch Suc.S., thus breaking the circuit for the safety switch heater SSH.Accordingly the bimetal latch 48 will not unlatch and the safety switchwill remain closed. If there is an initial failure of suction, however,caused by a. broken belt, improper operation of the motor, jamming ofthe blower or the like, then the suction switch will remain closed andthe safety switch heater, after being energized fora period of time, forinstance, thirty seconds, will warp the bimetal latch 48 to an unlatchedposition thereby permitting thesafety switch SS to open and accordinglystop operation of the burner system because of de-energization of therelay coil RC. The trouble must then be remedied and the safety switchreset in closed position. If suction fails after being. established, dueto failure of the motor or blower or breakage of the belt 6| or thelike, then the suction switch will close resulting in a re-energizationof the safety switch heater so that after a time period the safetyswitch will open and shut down the system.

Thus I provide a protection system for the burner which operates to shutdown the system after a time period in response to either initial orsubsequent suction failure from any cause resulting in reversion of theair in the conduit 51 to atmospheric pressure. The time delay periodpermits starting of the burner while the proper suction is being builtup in the conduit 58. Otherwise, immediate opening of the safety switchSS because of the suction switch being normally closed, would preventstarting.

The limit switch serves as a means to open the room thermostat circuitand therefore shut down operation of the burner whenever the roomthermostat calls for heat beyond a safe temperature of the furnace.After the limit switch opens, if the furnace temperature falls to aposition permitting the limit switch to again close while the roomthermostat is still closed, there will be another burner operation whichwill be discontinued either by the room thermostat in response tosufficient rise in temperature in the room or in response to excessivetemperature of the furnace again opening the limit switch. Thus thelimit 'switch guards against excessive furnace temperature while thesuction switch guards against either initial failure of suction orfailure thereof after suction has been established.

As long as the pilot light I4 is burning, the gas valve GV will beopened whenever the motor M is energized. In the event of combustionfailure of the burner I1 and extinguishment of the pilot flame I8,however, then the thermostat l5 will open the switch l6 so that gas willcease flowing to the burner. In this way provision is made in aconventional manner for preventing continued flow of fuel to the burnerwhen ignition fails due to the pilot flame l8 becoming extinguished ordue to the pilot burner becoming sootladen or otherwise inoperative.

Various modifications can be made in the construction and arrangement ofthe parts of my burner control apparatus and protection system withoutdeparting, however, from the real spirit and purpose of my invention;Therefore, I intend to cover by my claims any modified forms ofstructure or use of mechanical equivalents which may be reasonablyincluded within their scope.

I claim as my invention.

1. In a burner control apparatus and protection system for a burnerhaving an induction blower, a room thermostat, a relay operable uponenergization to cause operation of the burner and v the inductionblower, a control circuit for said relay controlled by said roomthermostat, said room thermostat establishing said control circuit uponclosure of the room thermostat, said control circuit including a safetyswitch, means to open said safety switch after a time period, a. switchresponsive to suction of said induction blower and operable to rendersaid means to open said safety switch inoperative upon a substantialvacuum being produced by said induction blower and another controlcircuit to stop flow of fuel to the burner upon combustion failureeither initially or subsequent to establishment.

4 2. In a burner apparatus and protection system for a burner having aninduction blower, a

transformer, a room thermostat, a relay operable switch responsive tothe suction of said induction blower, said suction switch being incircuit with the remaining portion of said secondary and being normallyclosed, said suction switch opening and thereby rendering said actuatorinoperative upon a substantial vacuum being produced by said inductionblower and means to stop the flow of fuel to the burner upon combustionfailure.

3. In a burner control apparatus and protection system for a burnerhaving an induction blower and means to stop the flow of fuel as aresult of combustion failure, a control circuit for the burner andblower to cause operation thereof when the control circuit is closed, aroom thermostat, a safety switch and a safety switch actuator in saidcontrol circuit and a suction switch responsive to the suction of saidinduction blower, said suction switch being also in said circuit andoperable to lie-energize said safety switch actuator when said suctionswitch responds to a vacuum produced by said induction blower.

4. In combination with a burner having means to stop the flow of fuelupon combustion failure and an induction blower, a safety switch, meansfor opening said safety switch after a time period and means forretaining said last means inoperative upon suction being established bysaid induction blower comprising a switch in the operating circuit ofsaid safety switch, said last switch being responsive to such suction.

5. A burner control apparatus for a burner having means to stop the flowof fuel thereto ported for movement relative to said conduit,

means biasing said disc to remain in a predetermined position relativeto said conduit at which position said safety switch is in operation andwhereby a change in. pressure in said conduit on opposite sides of saiddisc causes the disc to move to another position against its bias andthereupon change the position of the suction switch, said changedposition of said suction switch causing it to render said safety switchinoperative.

BURTON E. SHAW.

